Airworthiness Directive · Amendment 39-17628 · -13-p
AgustaWestland S.p.A. (Agusta) Helicopters
This AD applies to the following Agusta S.p.A. (Type certificate currently held by AgustaWestland S.p.A) (Agusta) helicopters, with a tail rotor drive shaft flexible disc coupling (Thomas coupling) nut, part number (P/N) MS21042L4, certificated in any category:
(i) Model A109A, A109A II, A109C, A109E, A109S, A109K2, AW109SP helicopters; and
(ii) Model A119 and AW119 MKII helicopters.
We are adopting a new airworthiness directive (AD) for Agusta Model A109A, A109A II, A109C, A109E, A109K2, A109S, AW109SP, A119, and AW119 MKII helicopters. The emergency AD was sent previously to all known U.S. owners and operators of these helicopters. This AD requires, before further flight, inspecting certain Thomas coupling nuts on the tail rotor drive shaft line for a crack and replacing all the nuts if any nut is cracked. Also this AD requires replacing all affected Thomas coupling nuts within 10 hours time-in-service (TIS) or 30 days, whichever occurs first. This AD was prompted by two incidents of cracking on the nuts that connect the flexible disc coupling (Thomas coupling) with the splined adapter on the tail rotor drive shaft. We are issuing this AD to correct the unsafe condition on these helicopters.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
(1) Before further flight, using a borescope or light source and mirror, inspect each Thomas coupling nut for a crack. If any Thomas coupling nut is cracked, before further flight, replace all the Thomas coupling nuts with nuts, P/N NAS1805-4, torqueing each nut to 5.6-7.9 Nm.
(2) Within 10 hours time-in-service or 30 days, whichever occurs first, replace each Thomas coupling nut, P/N MS21042L4, with a nut, P/N NAS1805-4, torqueing each nut to 5.6-7.9 Nm.
(3) After the effective date of this EAD, do not install a nut, P/N MS21042L4, on any Thomas coupling.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
